The invention generally relates to semiconductor fabrication, and particularly to semiconductor memory devices providing improved memory performance within a high density memory layout.
Recently, system-on-chip (SoC) technology provides reduced development cycle time while increasing product functionality, performance and quality. SoC technology allows placement of multiple function “subsystems” on a single semiconductor chip. The various types of subsystems that may be integrated within the semiconductor chip include microprocessor and micro-controller cores, digital signal processors (DSPs), memory blocks, communication cores, sound and video cores, radio frequency (RF) cells, power management, and high-speed interfaces, among others. SoC technology can thus provide customized products for a variety of applications, including low-power, wireless, networking, consumer and high-speed applications.
Typically, integration of memory in SoC technology is complicated due to the incompatibility of memory process with the logic process and a need for larger surface area of the memory cell array. In addition, to address requirements for transistors that are as fast as possible, and thus, have feature sizes as small as possible, many processes employ gate conductors having critical dimension less than 1.0 μm, reducing feature size of resulting transistors. Fabrication of reduced-size transistors in SoC technology allows more transistors to be placed on a substrate, allowing relatively large circuit systems to be incorporated onto single, relatively small semiconductor chips. Moreover, as transistor feature sizes continue to decrease with advancements in manufacturing, more memory cells can be incorporated onto the chip without increasing chip area. In many SoC applications, this may be especially advantageous in increasing on-chip memory, but disadvantageous in increasing memory cell device leakage directed to the size-reduced transistors.
Thus, minimized memory cell device leakages with optimal size-reduction of the transistors is needed.